1. Field of the Invention
The present invention relates broadly to the application of a hard, abrasive coating to a metal substrate. In particular, the invention relates to means and methods for applying a coating comprising diamonds to a metal substrate using conventional gas and electric welding or brazing techniques.
2. State of the Art
It has been known to apply a hardfacing to a metal substrate by brazing a coating containing carbide particles such as tungsten carbide to the metal substrate. Brazing rods are available commercially that can be used to braze a coating containing carbide particles to a metal substrate. A & B Metal Mfg. Company, Inc. of Houston Tex. and Kennametal Inc. of Latrobe, Pa. produce and sell tungsten carbide brazing rods. The tungsten carbide brazing rods are used to apply a coating of abrasive material to drilling tools to increase their life. The drilling tools are commonly made with a diamond cutting surface. When the diamond surface becomes impaired, such as by loss of diamond particles, the coating of carbide particles to the tool will increase its life somewhat. It would be highly advantageous and desirable if the diamond coating could be replaced on the tool. The tool would then be capable of its full cutting ability.
There has been no suggestion in the prior art of being able to braze a coating containing diamond particles to a metal substrate such as a drilling tool. There are various processes that are known used for depositing a layer of braze containing diamond particles on a metal substrate. All such methods universally require controlled heating of the substrate in a vacuum furnace. There is no suggestion of brazing a coating of braze material containing diamond particles on the metal substrate using conventional gas or electric welding and brazing techniques.
In U.S. Pat. No. 5,100,045 issued to Ronald C. Wiand on Mar. 31, 1992, a method of reconditioning brazed diamond abrasive tools is disclosed. It is recognized in that patent that it would be highly desirable to be able to recondition or repair brazed diamond abrasive tools. Unfortunately, the method taught in U.S. Pat. No. 5,100,045 the tool that is repaired is placed in a vacuum furnace and heated to a temperature of about 1900.degree. F. or at least about 70.degree. F. above the liquid melting point or flow point of the braze. The old braze becomes thermoplastic and the diamond particles reorient to present new abrading edges. If the tool has bare or bald spots on the tool, i.e., spots where the original diamond particles have broken away and are no longer present, new brazing powder and a binder are mixed to form a brazing paste which is placed on the tool to cover the bald spots prior to the heating of the tool in the furnace. Diamond particles are placed on the paste, and then the tool is heated in the vacuum furnace. The new and old braze becomes thermoplastic and the old and new diamonds reorient to present abrading edges and the brazes flow together. There is no suggestion of using a braze rod containing a braze and diamond particles, wherein the braze is applied directly to the surface of the tool using conventional gas and electric welding and brazing techniques.